1. Field of the Invention
The present invention relates to an imaging system capable of outputting, as image information, a photoelectrically converted electric signal from a pixel arbitrarily specified as a read target from among a plurality of pixels for imaging.
2. Description of the Related Art
In a medical field, an endoscope system has conventionally been used for observing an organ of a subject such as a patient. The endoscope system includes an imaging device (electronic scope) that has flexibility and an elongated shape and is configured to be inserted into a body cavity of the subject, an image pickup device that is provided at a distal end of the imaging device and captures an in-vivo image, a light source device that emits illumination light to illuminate the subject, a processing device (external processor) that performs specified image processing on the in-vivo image captured by the image pickup device, and a display device capable of displaying the in-vivo image that has been subjected to the image processing by the processing device. In acquiring the in-vivo image using the endoscope system, after an insertion unit is inserted into the body cavity of the subject, the illumination light is emitted from a distal end of the insertion unit to illuminate body tissue in the body cavity, and the image pickup device captures the in-vivo image. A user such a doctor observes an organ of the subject based on the in-vivo image displayed on the display device.
A CMOS (Complementary Metal Oxide Semiconductor) sensor can be used as the image pickup device to be provided in such an endoscope system. A CMOS sensor generates image data according to a rolling shutter method in which exposure or readout is carried out for each line at different timings.
Further, in order to prevent degradation in image quality due to exposure unevenness between the lines of the image pickup device, there is known a technique in which lighting and light extinction of illumination are performed in a specified cycle under a PWM (Pulse Width Modulation) control in synchronization with the exposure cycle or readout cycle of the image pickup device (see Japanese Laid-open Patent Publication No. 2007-318581).